Previous work in this program project has identified motions that are involved in the catalytic function of enzymes. The hypothesis for our work in this renewal application is that by using theoretical and computational methods we can identify the structural elements that create dynamics related to catalysis on all timescales, and through these means we may create protein dynamics design paradigms for both rate enhancement, and enzyme inhibition. In order to complete this research program we will work on 5 distinct areas that are: 1) we will identify conformational movements necessary on all timescales for reaction. Just as we have followed trajectories and identified protein dynamics that form promoting vibrations and are part of the reaction coordinate, we will extend these calculations to the timescale of enzyme turnover. 2) We will identify structural elements in specific enzyme systems (lactate dehydrogenase and purine nucleoside phosphorylase) that create the specific dynamics. 3) We will identify allosteric binding sites and determine the effect of binding on protein dynamics. 4) We will identify how dynamics is involved in transition state inhibitor binding. 5) we will propose a redesign of heavy PNP that corrects dynamic defects we have previously identified and restores normal catalytic function. The overall thrust to all of the work in this program project has been the identification of dynamics as a central feature in enzyme function from the selection of a catalytically competent conformational substate to rapid promoting vibrations. We now proceed to the next step in this program - identification of dynamics as a design element in enzyme function. We propose to begin the process of developing this concept as a protein engineering tool.